The embodiments herein relate to methods for hindering the settling of particulates in a subterranean formation.
Subterranean wells (e.g., hydrocarbon producing wells, water producing wells, and injection wells) are often stimulated by hydraulic fracturing treatments. In a typical hydraulic fracturing treatment, a treatment fluid is pumped into a wellbore in a subterranean formation at a rate and pressure above the fracture gradient of the particular subterranean formation to create or enhance at least one fracture therein. “Proppant” or “proppant particulates” (e.g., graded sand, bauxite, ceramic, nut hulls, and the like) are typically suspended in a treatment fluid and deposited into the fracture(s) while maintaining pressure above the fracture gradient. The proppant particulates are generally deposited in the fracture(s) in a concentration sufficient to form a pack of proppant particulates, or a “proppant pack,” which serves to prevent the fracture from fully closing once the hydraulic pressure is removed. By keeping the fracture from fully closing, the interstitial spaces between individual proppant particulates in the proppant pack form conductive pathways through which produced fluids may flow.
A known alternative hydraulic fracturing treatment involves placing a reduced volume of proppant particulates in a fracture to create a more conductive fracture. In such treatments, individual proppant particulates are formed into proppant aggregates. As used herein, the term “proppant aggregate” refers to a coherent body of any proppant particulates, such that the proppant aggregate does not tend to disperse into smaller bodies without the application of shear. The proppant aggregates may be placed into the fracture(s) in a spaced apart fashion, to form proppant pillars capable of maintaining sufficient integrity to hold open the fracture once the hydraulic pressure is removed and allow for the flow of produced fluids. The individual proppant pillars exist apart from the other proppant pillars, rather than forming a traditional proppant bed wherein each proppant particulate is nestled against neighboring proppant particulates. In this way, there is more space between the pillars for fluids to flow, rather than only being able to flow between the interstitial spaces of neighboring particles in a traditional bed. As used herein, the term “proppant” or “proppant particulates,” in all of its forms is intended to encompass proppant aggregates.
During hydraulic fracturing, other particulates may be suspended within the treatment fluid (e.g., weighting agents, bridging materials, and the like). These particulates are included in the treatment fluid to ensure that the treatment fluid is adequate to perform its given function and may vary depending on, for example, the conditions of the subterranean formation. As used herein, the term “particulate” is collectively used to refer to these particulates, as well as proppant particulates and proppant aggregates.
The specific gravity of particulates used in a subterranean operation may be high in relation to the treatment fluids in which they are suspended for transport and/or deposit in a fracture. As such, the particulates may settle out of the treatment fluids at any point during a subterranean operation. For example, the particulates may settle to the bottom of a wellbore or may form a heterogeneous gradient throughout the treatment fluids. Additionally, the particulates may settle out of the treatment fluid prior to reaching their intended target zone, thereby reducing their effectiveness in the treatment fluid. Proppant particulates may settle out of a treatment fluid toward the bottommost portion of the fracture, for example, resulting in complete or partial occlusion of the portion of the fracture where no proppant particulates have collected when the hydraulic pressure is removed (e.g., at the top of the fracture or a bottom portion of the fracture above a bottommost portion). Additionally, screenout may result, in which the particulates form a bridge across perforations or other restricted flow areas in a fracture resulting in fluid pathway blockage and prevention of fracture growth. As such, the productivity of a subterranean formation may be impaired due to settling of the particulates.